Boiler, it works different in a civil case than it does a criminal case. During a civil trial you aren't in jeopardy of going to jail so pleading the fifth is treated as a confession because you're choosing not to challenge the evidence presented against you.
That's why I said above an attorney would only advise a client to take the fifth in a civil proceeding if the client was facing significant criminal liability by answering the questions presented truthfully. Essentially, the AG in New York could request that the Trump organization be given the corporate death penalty. So millions of dollars are at stake and Trump chose not to defend himself. A rational person would only do that if they knew answering the questions truthfully would land them in prison.